JPS6074892A - Video camera - Google Patents

Abstract

PURPOSE:To attain reproduction for a reproduction picture in an optimum white balance state by using plural signals obtained by sampling the electric signals outputted from an image pickup device at plural points having time intervals respectively to decide the white balance. CONSTITUTION:When an image pickup button is pushed, a control circuit 27 samples and quantizes color difference signals S4 and S5 by A/D converters 21 and 22 at specific time intervals to store them to a memory circuit 30. When the circuit 30 is overflowed, the oldest signal is erased to memorize a new signal. The circuit 27 calculates the mean value of each digitized color different signal stored in the circuit 30 every time a new signal is stored to the circuit 30. The mean value is defined as S23 and S24 respectively to undergo D/A conversions 26 and 28 and the result is compared with the outputs of reference voltage generating circuits 25 and 29. Then comparison signals S33 and S34 are outputted. Then the circuit 27 sends outputs S18 and S19 of A/D converters 15 and 19 to gain control circuits 6 and 7 while monitoring signals S33 and S34 to control the gains of color difference signals S1 and S3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video camera with an automatic white balance adjustment device.

A white balance adjustment device for a video camera is essential. However, this adjustment method is made before shooting, and there is a high possibility that important camera opportunities will be missed. Furthermore, even though they are called automatic white balance systems, conventional ones perform the adjustment by pressing a button, so there are many failures due to forgetting to adjust the white balance.

An example of a circuit of a conventional automatic white balance adjustment device is shown in FIG. Blue signal S from terminal 1, brightness signal S from % terminal 2
2. Red signal s3 is input from terminal 3. The green signal S□ and the red signal s3 are gain-controlled by the gain control circuit 6.7, and then mixed with the luminance signal s2 by the subtraction circuit 8.9 to form the BY signal S and the RY signal S5. be done.

S4 and 85 are converted into video signals and output to the outside. S4, Ss are smoothed by smoothing circuit 10.12, and S8,
S, and the reference voltage signal S, from the reference voltage generator 11 at the comparators 13 and 14. , 811 and output comparison signals SI2 and S13, respectively. When the video camera is pointed at a white subject to adjust the white balance and the switch 20 is pressed, S20 becomes the ground level, and the control circuit 17 is notified that the white balance adjustment is to be started. It consists of a 16.18i up-down counter. S14 and 815 are signals that inform 16.18 that the white balance is being adjusted. 16 and 18 are initially set at the start of white balance adjustment. Si6 and Si7 are bit output signals of the up/down counter output from 16 and 18. 816
and 81□ are input to D7-A converters 15 and 19, respectively, and converted into gain setting analog signals S's and 819,
Input to gain control circuits 6 and 7.

The up/down counters 16 and 18 are turned up and down by the clock signal, and by controlling the gains of the gain control circuits 6 and 7, S8, Slo s Sg, and Sll are monitored while monitoring the comparison signals S12, S, and S. Set the logical value of the bit output signal of the up/down counter so that they match and latch it.

After adjusting the white balance in this manner, the adjustment value is locked and photographing is performed. Therefore, in the conventional example, it is necessary to always carry a white paper for adjusting the white balance every time a photograph is taken. Furthermore, it is necessary to readjust the white balance every time the shooting conditions change, making fine-grained adjustments impossible.

The present invention eliminates such drawbacks and its purpose is to provide a real-time, fully automatic white balance adjustment device.

The present invention will be described in detail below based on Examples.

FIG. 2 shows an embodiment according to the present invention. 21 and 22 are A
-D converter. The switch 31 is synchronized with the shooting switch of the video camera. When switch 31 is pressed,
The B-Y signal S4 and the R-Y signal S are A-D converted at specific time intervals to become S21 and 82□, and the control circuit 2
Enter 7. 30 is a memory circuit. 50 stores a plurality of digital signals that have been A-D converted at specific time intervals. One embodiment according to the present invention is a control circuit 2
7 can be divided into two circuit systems and explained. The first circuit system is concerned with the digitization and storage of the color difference signals S4 and 85. The second circuit system is related to calculating the average value of the digital signal and correcting the white balance.

First, the first circuit system will be explained. When the shooting start button is pressed, the switch 31 synchronized with the button is turned on, and the control circuit 27 instructs the A-D converters 21 and 22 to sample and quantize the color difference signals S4 and 85 at specific time intervals. issue instructions to. The quantized color difference signals S21 and 82□ are controlled by the control circuit 27 and stored in S30 and the storage circuit 60. The control circuit 27 controls the storage circuit 60 to sequentially store the quantized color difference signals in the storage circuit 50, and when the storage circuit 60 overflows,
Erase the oldest signal and store the next new signal. Next, the second circuit system will be explained.

Every time a new signal is stored in the storage circuit 60, the control circuit 27 calculates the average value of each of the digitized color difference signals stored in the storage circuit 30.

The average values are Si3, S2, Itotosu D-A, respectively.
The signals are sent to converters 26 and 28 and converted into analog signals.

25 and 29 are reference voltage generation circuits.

Signals 825 and 828 outputted from 25 and 29 are reference signals for setting white balance and are set to optimal values in advance. Comparators 26 and 24 compare S25 and 826 and S27 and 828, respectively, and output comparison signals 833 and 834. The control circuit 27 monitors S33 and S34 and controls the D-A converters 26 and 2 so that the inputs of the respective comparators almost match.
The digital signals of S23 and 824 are sent to the terminals 8 and 8, respectively. Next, the difference between the average value of the digital color difference signals initially sent to the DA converters 26 and 28 and the digital signal sent so as to match the reference voltage signals S26 and 8211 is determined by the control circuit 27 at step S2. and S3□, respectively, to the A-D converters 15 and 19.

The output signals StS and 819 of the A-D converters 15 and 19 are input as white balance adjustment signals to the gain control circuits 6 and 7, and the gains of the color difference signals S and 83 are controlled to adjust the white balance.

According to the present invention, the white balance can be adjusted in real time, so even if the shooting situation changes, corrections can be made to the white balance one after another. Furthermore, since there is no possibility of forgetting to make adjustments, there are fewer mistakes in shooting. Since the adjustment is made using the temporal average value of the photographed signal, there is no need to provide a filter or sensor for white balance iJ, and a simple video camera configuration is possible.

Further, the circuit for realizing the present invention can be easily constructed by a semiconductor circuit, and has excellent effects such as not causing a cost increase. Furthermore, the present invention is not limited to the above-mentioned digitizing embodiments.
It is also possible to average the video signal analogously.

Application examples of the present invention include not only video cameras but also a wide range of applications such as video tape recorders, television playback devices, etc. In the case of video tape recorders, television playback devices that automatically adjust the white balance of recorded signals In this case, it becomes possible to reproduce a reproduced image in an optimal white balance state.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional white balance adjustment device. FIG. 2 is a circuit diagram of a white balance adjustment device according to the present invention. 4... Output terminal for the B-Y signal 5... Output terminal for the R-Y signal S31... Signal that informs the control circuit 27 of the start of white balance adjustment. Suwa Seikosha Company Patent Attorney Tsutomu Mogami

Claims (1)

[Scope of Claims] 1) In a video camera including at least an imaging section that converts light into an electrical signal and an optical section that guides light to the imaging section, the white balance of the video camera is determined based on the imaging section. 1. A video camera with an automatic white balance adjustment device, characterized in that the video camera is configured to be determined by a plurality of signals obtained by sampling an electrical signal outputted from a device at a plurality of points having time intervals. 2) The white balance is configured to be determined by the average value of a plurality of signals obtained by sampling electrical signals output from the imaging unit at a plurality of points having time intervals. Video camera with automatic white balance adjustment device. 6) Sampling the electrical signal output from the imaging unit,
A video camera with an automatic white balance adjustment device according to claim 1 or claim 2, further comprising a storage element for storing the quantized logic signal.